Outside forces like the U.S. can make the difference, but timing matters
It's odd, but not necessarily surprising, that critics of the Libya intervention were calling it any number of things: mistake, quagmire, dangerous, an Iraq repeat, and so on. It is odd because the ultimate outcome -- the rebels winning and Qaddafi falling -- never seemed much in doubt. It was a matter of when, not if. For both better and worse, Libya confirms the reality that the role of external actors (in this case, the United States and Europe) can still be decisive in the Arab struggle for freedom.
We should always tread carefully with counterfactuals. But it is difficult to deny that the alternative to doing something -- doing nothing -- would almost certainly have led to a bloody, tragic massacre in Benghazi and other pockets of rebel resistance. Libya would have likely been held up as one of the great tragedies of Western neglect or outright subversion, on par with Iran in 1953 or Algeria and Iraq in the early 1990s. When you have the ability to act, doing nothing is no longer a neutral position.
To be sure, this is not a time for settling scores. But it is a time for arguing for the utility, necessity, and morality of a doctrine -- the Responsibility to Protect -- that seemed, to its opponents, increasingly discredited. Another reality -- again, for both better and worse -- is that the United States remains something of an "indispensable nation," a notion increasingly in disrepute. Without American support, however belated, the responsibility to protect would have remained mere rhetoric and posturing. The NATO intervention would not have happened.